U.S. patent application number 12/677003 was filed with the patent office on 2010-12-23 for shaft for golf club.
This patent application is currently assigned to MRC COMPOSITE PRODUCTS CO., LTD.. Invention is credited to Tetsuya Atsumi, Tsutomu Ibuki, Takashi Kaneko, Kouji Shiga.
Application Number | 20100323810 12/677003 |
Document ID | / |
Family ID | 40451993 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100323810 |
Kind Code |
A1 |
Kaneko; Takashi ; et
al. |
December 23, 2010 |
SHAFT FOR GOLF CLUB
Abstract
A shaft for a golf club comprises a plurality of
fiber-reinforced resin layers. A plurality of circumferentially
oriented metal wires are provided at intervals of 1 mm to 4 mm in
an axial direction of the shaft having a length in an axial
direction of more than 100 mm and less than 300 mm and being
centered at a position of 3.25.times.10.sup.2 mm from a
larger-diameter end of the shaft.
Inventors: |
Kaneko; Takashi;
(Toyohashi-shi, JP) ; Shiga; Kouji;
(Toyohashi-shi, JP) ; Atsumi; Tetsuya;
(Toyohashi-shi, JP) ; Ibuki; Tsutomu;
(Toyohashi-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
MRC COMPOSITE PRODUCTS CO.,
LTD.,
Toyohashi-shi
JP
|
Family ID: |
40451993 |
Appl. No.: |
12/677003 |
Filed: |
September 10, 2008 |
PCT Filed: |
September 10, 2008 |
PCT NO: |
PCT/JP2008/066299 |
371 Date: |
March 8, 2010 |
Current U.S.
Class: |
473/320 ;
473/319 |
Current CPC
Class: |
A63B 53/12 20130101;
A63B 60/06 20151001; A63B 2209/023 20130101; A63B 2209/02 20130101;
A63B 53/10 20130101; A63B 60/10 20151001; A63B 60/42 20151001; A63B
60/08 20151001; A63B 60/00 20151001 |
Class at
Publication: |
473/320 ;
473/319 |
International
Class: |
A63B 53/10 20060101
A63B053/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2007 |
JP |
2007-234023 |
Claims
1. A shaft for a golf club comprising: a plurality of
fiber-reinforced resin layers; and a plurality of circumferentially
oriented metal wires which are provided at intervals of 1 mm to 4
mm at such a portion of the shaft having a length in an axial
direction of more than 100 mm and less than 300 mm and being
centered at a position of 3.25.times.10.sup.2 mm from a
larger-diameter end of the shaft.
2. The shaft according to claim 1, wherein the plurality of
circumferentially oriented metal wires are provided at intervals of
1 mm to 4 mm at such a portion of the shaft having a length in an
axial direction of more than or equal to 160 mm and less than or
equal to 240 mm and being centered at a position of
3.25.times.10.sup.2 mm from the larger-diameter end of the
shaft.
3. The shaft according to claim 1, wherein the plurality of
circumferentially oriented metal wires are provided at intervals of
1 mm to 4 mm at such a portion of the shaft having a length in an
axial direction of 240 mm and being centered at a position of
3.25.times.10.sup.2 mm from the larger-diameter end of the
shaft.
4. The shaft according to claim 1, wherein the metal wire has a
flat cross section, a maximum thickness of 17 .mu.m to 25 .mu.m and
a width of 180 .mu.m to 280 .mu.m.
5. The shaft according to claim 1, wherein the metal wire is an
amorphous metal wire having tensile strength of 200 to 400
kgf/mm.sup.2, a degree of elongation of 1 to 3.5%, and Young's
modulus of 14000 to 17000 kgf/mm.sup.2.
6. A shaft for a golf club comprising a plurality of
fiber-reinforced resin layers, wherein the shaft satisfies the
following conditions (A) to (C): (A) bending rigidity of a portion
of 125 to 175 mm from a larger-diameter end of the shaft is
5.7.times.10.sup.6 kgfmm.sup.2 or less; (B) bending rigidity of a
portion of 225 to 275 mm from the larger-diameter end of the shaft
is 5.3.times.10.sup.6 kgfmm.sup.2 or more; and (C) when a test
piece having a width of 20 mm which is a portion of 345 mm to 365
mm from the larger-diameter end of the shaft is cut from the shaft,
and then a compression load is applied to the test piece,
crush-deformation resistance calculated from a straight portion of
a load-deformation graph is 2.3 to 2.6 kgf/mm.sup.2.
Description
TECHNICAL FIELD
[0001] The present invention relates to a shaft for a golf
club.
[0002] The present application claims priority from Japanese Patent
Application No. 2007-234023, filed on Sep. 10, 2007, the contents
of which are hereby incorporated by reference into this
application.
BACKGROUND ART
[0003] In order to improve the flying distance of a hit ball in
golf, the use of a long-sized golf club which has a long shaft for
golf club is effective. Hereinafter, the "shaft for golf club" is
referred to as a "shaft". If the long-sized golf club is used, the
head speed is increased at the time of the swing of the golf club;
therefore, the flying distance is extended.
[0004] However, if a long-sized golf club is used, since the
position the ball is hit in is distant from the grip when compared
with a golf club of a common length, there is a problem in that the
possibility of miss-hitting the ball increases.
[0005] Recently, for the purposes of solving the miss-hitting by
the long-sized golf club, a long-sized golf club mounted with a
large-sized golf club head having a volume of over 400 cc
(hereinafter, referred to as a large head) has appeared and been
established in the market (see Patent Document 1). If a long-sized
golf club mounted with a large head is used, moment of inertia of
the head is increased and the directivity of the hit ball. In
addition, since the large head has a large sweet spot, the
miss-hitting is reduced. Moreover, since the large head provides
the user with a visual sense of ease, the user can execute their
swing in a more relaxed state compared with a case of using a
conventional long-sized golf club, thereby reducing the
miss-hitting.
[0006] However, compared with a conventional head, the mass of the
large head has been increasing. Further, if the length of the shaft
is simply lengthened, the mass of the shaft increases with the
extended length. Therefore, the mass of the whole golf club
increases by assembling such a lengthened shaft to the large head,
and thus the moment of inertia of the whole golf club increases.
Since it is difficult to swing such a golf club, swing speed
decreases, and the flying distance of the ball may be
shortened.
[0007] In order to suppress the increase in moment of inertia of
the whole golf club in the long-sized golf club mounted with the
large head, it is necessary to suppress the increase in the mass of
the shaft. However, if the increase in the mass of the shaft is
suppressed and the thickness of the shaft is also reduced in order
to extend its length, the rigidity of the shaft is lowered, and a
deformation amount of the shaft then increases when hitting the
ball, thereby its controllability deteriorates. Consequently, the
directivity of the hit ball becomes prone to variation.
[0008] In order to solve the above problems, a golf club including
a shaft having a first outer diameter of 16.5 mm or more which is
extended to 100 mm from the grip side end is disclosed (see Patent
Document 2). By setting the first outer diameter of the shaft as
the above size, it is possible to suppress bending deformation and
torsional deformation in the shaft.
[0009] [Patent Document 1] Japanese Unexamined Patent Application,
First Publication No. 2000-325512
[0010] [Patent Document 2] Japanese Unexamined Patent Application,
First Publication No. 2000-300704
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0011] However, according to the golf club disclosed in Patent
Document 2, since the increase in the weight is suppressed and the
outer diameter of the shaft is increased, the thickness of the
shaft is thinned. A "crush deformation amount", in which the cross
section of the shaft is crushed into an oval shape at the time of
hitting the ball, tended to rather increase. Consequently, it is
not possible to sufficiently reduce the deformation amount of the
shaft. Further, there is a problem in that since the grip is
thicker than a conventional golf club, there are many players who
are bothered by a sense of discomfort.
[0012] The present invention is contrived taking the above
circumstances into consideration, and an object of the present
invention is to provide a shaft for a golf club which can reduce
the crush deformation amount, suppress increases in the weight of
the shaft, improve the flying distance of a hit ball, and reduce
variations in the directivity of the hit ball, even though the
length of the shaft is extended.
Means for Solving Problem
[0013] In order to solve the above problem, the present invention
employs the following configuration.
[0014] A shaft for a golf club of the present invention comprises a
plurality of fiber-reinforced resin layers and a plurality of
circumferentially oriented metal wires are provided at intervals of
1 mm to 4 mm in an axial direction at such a portion of the shaft
having a length in an axial direction of more than 100 mm and less
than 300 mm and being centered at a position of 3.25.times.10.sup.2
mm from a larger-diameter end of the shaft.
[0015] The plurality of circumferentially oriented metal wires may
be provided at intervals of 1 mm to 4 mm in an axial direction at
such a portion of the shaft having a length in an axial direction
of more than or equal to 160 mm and less than or equal to 240 mm
and being centered at a position of 3.25.times.10.sup.2 mm from the
larger-diameter end of the shaft.
[0016] The plurality of circumferentially oriented metal wires may
be provided at intervals of 1 mm to 4 mm in an axial direction at
such a portion of the shaft having a length in an axial direction
of 240 mm and being centered at a position of 3.25.times.10.sup.2
mm from the larger-diameter end of the shaft.
[0017] The metal wire may have a flat cross section, a maximum
thickness of 17 .mu.m to 25 .mu.m, and a width of 180 .mu.m to 280
.mu.m.
[0018] The metal wire may be an amorphous metal wire having tensile
strength of 200 to 400 kgf/mm.sup.2, a degree of elongation of 1 to
3.5%, and Young's modulus of 14000 to 17000 kgf/mm.sup.2.
[0019] Further, the shaft for the golf club of the present
invention is constituted of a plurality of fiber-reinforced resin
layers, and is characterized by satisfying the following conditions
(A) to (C):
[0020] (A) bending rigidity of a portion of 125 to 175 mm from the
larger-diameter end of the shaft is 5.7.times.10.sup.6 kgfmm.sup.2
or less;
[0021] (B) bending rigidity of a portion of 225 to 275 mm from the
larger-diameter end of the shaft is 5.3.times.10.sup.6 kgfmm.sup.2
or more; and
[0022] (C) when a test piece having a width of 20 mm which is a
portion of 345 mm to 365 mm from the larger-diameter end of the
shaft is cut from the shaft, and then a compression load is applied
to the test piece, crush-deformation resistance calculated from a
straight portion of a load-deformation graph is 2.3 to 2.6
kgf/mm.sup.2.
Effect of the Invention
[0023] According to the shaft for a golf club of the present
invention, there is provided a golf club in which even though the
length of the shaft is extended, since the crush deformation amount
is reduced and the increase in weight of the shaft is suppressed,
swing speed can be increased to improve the flying distance when
hitting a ball, and the controllability can be enhanced to reduce
variations in directivity of the hit ball.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a perspective oblique view schematically
illustrating an example of an embodiment of a shaft 10 for a golf
club according to the present invention.
[0025] FIG. 2 is a partial cross-sectional view of a reinforced
portion 3 of an example of the present invention.
[0026] FIG. 3 is a conceptual diagram of a drum winding device 20
used at fabrication of a metal wire prepreg in an example of the
present invention.
[0027] FIG. 4 is a view illustrating a cutting shape of a prepreg
used at fabrication of a shaft for a golf club in Example 1, and an
order of winding the prepreg around a cored mandrel 30.
[0028] FIG. 5 is an EI distribution illustrating a relation between
bending rigidity EI value and a distance from a larger-diameter end
of a shaft for a golf club in Comparative Example 1.
[0029] FIG. 6 is an EI distribution illustrating a relation between
bending rigidity EI value and a distance from a larger-diameter end
of a shaft for a golf club in Example 2.
[0030] FIG. 7 is an EI distribution illustrating a relation between
bending rigidity EI value and a distance from a larger-diameter end
of a shaft for a golf club in Example 3.
[0031] FIG. 8 is an EI distribution illustrating a relation between
bending rigidity EI value and a distance from a larger-diameter end
of a shaft for a golf club in Example 4.
[0032] FIG. 9 is an EI distribution illustrating a relation between
bending rigidity EI value and a distance from a larger-diameter end
of a shaft for a golf club in Comparative Example 2.
[0033] FIG. 10 is an EI distribution illustrating a relation
between bending rigidity EI value and a distance from a
larger-diameter end of a shaft for a golf club in Comparative
Example 3.
[0034] FIG. 11 is an EI distribution illustrating a relation
between bending rigidity EI value and a distance from a
larger-diameter end of a shaft for a golf club in Comparative
Example 4.
[0035] FIG. 12 is an EI distribution illustrating a relation
between bending rigidity EI value and a distance from a
larger-diameter end of a shaft for a golf club in Comparative
Example 5.
[0036] FIG. 13 is an EI distribution illustrating a relation
between bending rigidity EI value and a distance from a
larger-diameter end of a shaft for a golf club in Comparative
Example 6.
[0037] FIG. 14 is an EI distribution illustrating a relation
between bending rigidity EI value and a distance from a
larger-diameter end of a shaft for a golf club in Comparative
Example 7.
DESCRIPTION OF THE REFERENCE NUMERALS
[0038] 1 FIBER-REINFORCED RESIN LAYER [0039] 2 LARGER-DIAMETER END
[0040] 3 REINFORCED PORTION [0041] 4 AXIS [0042] 5 METAL WIRE
[0043] 7, 8 GLASS FIBER-REINFORCED RESIN LAYER [0044] 10 SHAFT FOR
GOLF CLUB
BEST MODE FOR CARRYING OUT THE INVENTION
[0045] An example of a shaft for a golf club according to the
present invention will now be described.
[0046] As shown in FIG. 1, the shaft 10 for a golf club has a
tubular structure, and the tubular structure is constituted of a
plurality of fiber-reinforced resin layers 1. At a portion
(hereinafter, referred to as a reinforced portion 3) extending from
a distance c from a larger-diameter end 2 of the shaft 10 to a
distance d from the larger-diameter end 2 of the shaft 10, a
plurality of circumferentially oriented metal wires 5 (vertical to
an axis 4 direction) are provided. As shown in FIG. 2, the metal
wires 5 are provided spaced apart from adjacent metal wires 5 in an
axial direction at an interval e so as not to contact with each
other. The term `larger-diameter end 2` means an end formed by
winding prepreg around a cored mandrel to form a shaft tube, curing
a resin in the prepreg, removing the cored mandrel, cutting both
ends of the shaft tube by 10 mm to form a shaft having a whole
length of 1170 mm, and then cutting the larger-end side of the
shaft by 75 mm at the time of fabricating a golf club.
[0047] The distance c is preferably more than 1.75.times.10.sup.2
mm and less than 2.75.times.10.sup.2 mm, more preferably,
2.05.times.10.sup.2 mm or more and 2.45.times.10.sup.2 mm or less,
even more preferably, 2.05.times.10.sup.2 mm. The distance d is
preferably more than 3.75.times.10.sup.2 mm and less than
4.75.times.10.sup.2 mm, more preferably, 4.05.times.10.sup.2 mm or
more and 4.45.times.10.sup.2 mm or less, even more preferably,
4.45.times.10.sup.2 mm. From the preferred range of the distance c
and the distance d, the reinforced portion 3 is preferably more
than 1.00.times.10.sup.2 mm and less than 3.00.times.10.sup.2 mm,
more preferably 1.60.times.10.sup.2 mm or more and
2.40.times.10.sup.2 mm or less, even more preferably,
2.40.times.10.sup.2 mm. The interval e of the adjacent metal wires
5 is preferably 1 mm or more and 4 mm or less.
[0048] The thickness of the fiber-reinforced resin layers 1 is not
particularly limited, but is preferably from 0.5 mm to 3.5 mm. The
thickness of each fiber-reinforced resin layer 1 is from about 0.01
mm to about 0.25 mm. The number of the layers forming the
fiber-reinforced resin layer 1 is not particularly limited, but
preferably is from 6 layers to 35 layers.
[0049] As a matrix resin constituting the fiber-reinforced resin
layer 1, a thermoplastic resin or a thermosetting resin may be
used.
[0050] As the thermoplastic resin, a polyamide-based resin, a
polyacrylate-based resin, a polystyrene-based resin, a
polyethylene-based resin, and a mixture resin thereof may be used.
As the thermosetting resin, an epoxy-based resin, an unsaturated
polyester-based resin, a phenol-based resin, a urea-based resin, a
melamine-based resin, a diallyl phthalate-based resin, a
urethane-based resin, a polyimide resin, and a mixture thereof may
be used. Preferably, the thermosetting resin is used, and the
epoxy-based resin is preferably used, since its curing shrinkage
ratio is low and it has a high rigidity and a high toughness.
[0051] As the reinforced fiber constituting the fiber-reinforced
resin layer 1, an inorganic fiber, such as metal fiber, boron
fiber, carbon fiber, glass fiber, ceramic fiber, an aramid fiber,
and other high-strength synthetic fibers are used. Since an
inorganic fiber is lightweight and has high strength, an inorganic
fiber is preferably used. Among them, the carbon fiber is more
preferably used, because of its high specific strength and specific
rigidity. These fibers may be used alone or in combination.
Further, a different reinforced fiber may be used for every layer,
and, for example, the fiber-reinforced resin layer 1 may be
configured by combining a carbon fiber layer and a glass fiber
layer. In addition, a fiber of any length, such as a long fiber, a
short fiber or a fiber mixture thereof may be used.
[0052] As one example of the fiber-reinforced resin layer 1, as
shown in FIG. 2, glass fiber layers 7 and 8 and a reinforced fiber
layer other than glass fiber may be combined. The glass fiber layer
7 is made of two-layered glass fiber woven fabric.
[0053] As the metal wire 5, a piano wire, a stainless steel wire, a
titanium wire, an amorphous metal wire or the like may be used.
Preferably, the amorphous metal wire is used, and its composition
is preferably Co/Fe/Cr/Si/B. The amorphous metal wire of such a
composition has superior strength and a low degree of elongation,
and little dimensional variation is produced at the fabrication.
Further, it has the same corrosion resistance as that of an SUS304
stainless steel wire.
[0054] The metal wire 5 may have a true-circle or flat cross
section, however a flat cross section is preferable. By making the
cross section of the metal wire 5 flat, the thickness of the layer
on which the metal wire is placed can be thinned. Therefore, when
the metal wire 5 is placed on the outermost layer which has the
most significant reinforcing effect, it does not interfere with the
role of the other fiber-reinforced resin layer 1. Further, since
the metal wire 5 having the flat cross section comes into surface
contact with the resin or fiber of the fiber-reinforced resin layer
1, peeling resistance is enhanced.
[0055] In the case in which the metal wire 5 have a flat cross
section, it has a cross section which is a convex and arch shape,
and preferably has a maximum thickness of 17 .mu.m to 25 .mu.m and
a width of 180 .mu.m to 280 .mu.m. The metal wire 5 having such a
cross section can be easily cut at a cut step in the process of
fabricating the shaft for the golf club, as compared with a
true-circle metal wire having the same reinforcing effect, thereby
enhancing the workability.
[0056] The metal wire 5 is preferably an amorphous metal wire
having tensile strength of 200 to 400 kgf/mm.sup.2, a degree of
elongation of 1 to 3.5%, and Young's modulus of 14000 to 17000
kgf/mm.sup.2. The metal wire 5 is advantageous as compared with
metal wires outside of the range in view of interlayer adhesion,
crush strength development, handling properties.
[0057] The reinforced portion 3 corresponds to a portion of the
shaft for the golf club in which crush deformation is large. By
disposing the plurality of metal wires 5 around the reinforced
portion 3, it is possible to reduce the crush deformation in the
reinforced portion 3.
[0058] The metal wire 5 may be positioned at any position between
plural layers constituting the fiber-reinforced resin layer 1. It
is preferable that the metal wire be positioned near the outermost
layer, since it further enhances the reinforcing effect.
[0059] The metal wires 5 are circumferentially oriented at
intervals e (1 mm to 4 mm) in the direction of axis 4 of the shaft
10 for the golf club. By setting the intervals of the metal wires
to 5 to 4 mm or less, the sufficient reinforcing effect can be
obtained. Further, by setting the intervals to 1 mm or more, it is
possible to prevent the weight of the shaft 10 for the golf club
from dramatically increasing. The interval e of the plurality of
metal wires 5 may be an equal distance or different distance.
[0060] The displacement number of the metal wires 5 is varied
according to the width of the metal wires 5, but 30 to 240 metal
wires 5 are preferable. If 240 or less, it is possible to prevent
the weight from dramatically increasing, and if 30 or more, the
sufficient reinforcing effect for the crush deformation can be
obtained.
[0061] The metal wires 5 are circumferentially oriented and placed.
That is, the metal wire 5 is formed in a circular ring. The metal
wires 5 are preferably formed in such a way that both ends thereof
are coupled to each other in a ring shape, but it is not necessary
to always couple both ends of the metal wires 5. A gap may be
formed between both ends, and it may be formed in any arc shape
having various degrees of arc (center angle).
[0062] Preferably, the metal wires 5 are interposed and disposed
between two glass fiber reinforced resin layers 7 using glass fiber
woven fabric as a reinforced fiber, as shown in FIG. 2. The glass
fiber woven fabric has a moderate undulation on its surface. At the
time of fabricating the shaft for the golf club, the undulation has
a role of preventing the fixed metal wires 5 from being shifted, so
that the intervals between the metal wires 5 are not changed.
[0063] As the glass fiber-woven fabric, the basis weight is
preferably from 20 g/m.sup.2 to 30 g/m.sup.2. The woven fabric
having the basis weight in such a range has undulation suitable for
shift prevention of the metal wires 5.
[0064] A method of pinching the metal wires 5 between the glass
fiber-reinforced resin layers 7 is not specially limited, but a
method of arranging a plurality of metal wires 5 evenly, overlaying
it with two-layered glass fiber woven fabrics which are previously
impregnated with matrix resin, and inserting it between a pair of
heated rollers to heat and compress it or a drum winding method
disclosed in Japanese Unexamined Patent Application Publication No.
2001-341126 may be exemplified.
[0065] At the outer layer of the glass fiber reinforced resin
layers 7, it is preferable that a glass fiber reinforced resin
layer 8 having a glass fiber as a reinforced fiber be further
formed. The glass fiber reinforced resin layer 8 can protect the
glass fiber reinforced resin layers 7 from being scratched by
grinding of the surface of the shaft tube, at a grinding process of
the surface of the shaft tube when fabricating the shaft for the
golf club.
[0066] In this instance, since the glass fiber reinforced resin
layers 7 and 8 are transparent resin layers due to properties of
the fiber, the metal wires 5 pinched in the glass fiber reinforced
resin layer 7 can be visually recognized from outside. Since the
shaft 10 for the golf club having such a configuration visually
shows this feature of the golf club to a user through the visual
recognition of the existence of the metal wires 5, it can form an
excellent decorative design for a golf club.
[0067] As described above, in the shaft 10 for the golf club
according to one embodiment of the present invention, since the
plurality of circumferentially oriented metal wires 5 are disposed
on the reinforced portion 3 at the interval e in the direction of
the axis 4, even though the length of the shaft is extended, the
increase in the weight of the shaft can be suppressed while the
crush deformation is reduced. Therefore, according to the golf club
using the shaft 10 for the golf club, since the increase in the
moment of inertia of the whole golf club is suppressed, the swing
speed can be enhanced, and thus the flying distance of the hit ball
can be improved. Also, since the controllability is improved, it
can reduce the variation in the directivity of the hit ball.
[0068] The configuration of the present invention is applied to a
shaft for a so-called long-sized and lightweight golf club, of
which the length is from 1143 mm to 1219 mm and the shaft has
weight of 40 g to 75 g, thereby exhibiting the effect
sufficiently.
[0069] The shaft 10 for the golf club of the present invention
having the above features exhibits the maximum effect by
combination of the large-sized head. As the large-sized head, a
combination with the large-sized head having a volume of 380
cm.sup.3 to 460 cm.sup.3 and moment of inertia of 3500 gcm.sup.2 to
5900 gcm.sup.2 is preferable as the large-sized head. The shaft 10
for the golf club of the present invention can suppress the
increase in the moment of inertia of the whole golf club, even
though a large-sized head is mounted.
[0070] In the shaft 10 for the golf club of the present invention,
it is preferable that bending rigidity of a portion of 125 to 175
mm from the larger-diameter end of the shaft be 5.7.times.10.sup.6
kgfmm.sup.2 or less, and bending rigidity of a portion of 225 to
275 mm from the larger-diameter end of the shaft be
5.3.times.10.sup.6 kgfmm.sup.2 or more.
[0071] The bending rigidity EI is measured by installing a fulcrum
point (a radius of a support jig installed at the fulcrum point:
12.5 mm) at a position of 150 mm toward the larger-diameter end
side and at a position of 150 mm toward a smaller-diameter end side
with centering a measuring point, increasing a load to the
measuring point (a radius of a load indenter jig installed at the
measuring points: 75 mm), and measuring deformation .delta..sub.10
(mm) and .delta..sub.20 (mm) of the shaft when the load of 10 kgf
and 20 kgf are applied, on the basis of the following equation. In
the bending rigidity distribution, the bending rigidity EI was
measured over the overall length whenever the measuring point is
moved at a constant interval of 50 mm in a longitudinal direction
of the shaft.
[0072] The bending rigidity EI can be obtained by using the
following equation.
EI=(.DELTA.P/L.sup.3)/(48.delta.)
[0073] EI: bending rigidity (kgfmm.sup.2)
.DELTA.P: 20 kgf10 kgf=10 kgf
[0074] L: distance (mm) between fulcrum points
[0075] .DELTA..delta.: .delta..sub.20-.delta..sub.10 (mm)
[0076] In the shaft 10 for the golf club of the present invention,
it is preferable that a test piece having a width of 20 mm which
centers a position of 355 mm from the larger-diameter end 2 of the
shaft 10 be cut, and a crush-deformation resistance (Rc) of the
test piece be 2.3 to 2.6 kgf/mm.sup.2. Regarding the value of the
crush-deformation resistance (Rc), the test piece having the width
of 20 mm which centers the position of 355 mm from the
larger-diameter end 2 of the shaft 10 is cut, and then when
compression load (P) is applied to the test piece in a direction
perpendicular to the axial direction of the specimen, the
deformation (.DELTA..lamda.) of the test piece is measured to
prepare a graph of load P-deformation .lamda.. At a straight
portion of the graph, .DELTA.P and .DELTA..lamda. are obtained, and
the crush-deformation resistance (Rc) is calculated by using the
following equation.
Rc=.DELTA.P/(.DELTA..lamda..times.w)
[0077] Rc: crush-deformation resistance (kgf/mm.sup.2)
[0078] .DELTA.P: load variations (kgf)
[0079] .DELTA..lamda.: crush deformation (mm)
[0080] w: width of test piece (20 mm)
[0081] In the shaft 10 for the golf club, it is preferable that the
test piece having the width of 20 mm which centers the position of
355 mm from the larger-diameter end 2 of the shaft 10 be cut, and
the crush-deformation resistance (Rc) of the test piece is 70 to 85
kgf.
[0082] The crush-deformation resistance (P3) is a load when the
test piece is broken by applying the compression load to the test
piece in a direction perpendicular to the axial direction of the
test piece. The value of the crush-deformation resistance (P3) is
obtained by measuring the load when the test piece is broken down
by cutting the test piece having the width of 20 mm which centers
the position of 355 mm from the larger-diameter end 2 of the shaft
10, and applying the compression load to the test piece in a
direction perpendicular to the axial direction of the specimen.
[0083] In a specific position of the shaft 10 for the golf club, in
the case in which the bending rigidity and the crush-deformation
resistance are within the above-described numerical range, since it
is possible to reduce the deformation of the shaft at the time of
hitting the ball and appropriate bending can be obtained, the
controllability of the golf club can be obtained, and thus the
variation in the directivity of the hit ball can be reduced. Even
though the length of the shaft is extended, the same effect can be
obtained. In addition, in the case in which the crush-deformation
resistance is within the numerical range, the effect is further
improved.
[0084] In the case in which the bending rigidity and the
crush-deformation resistance are not within the above-described
numerical range, since the deformation of the shaft is not reduced,
it is difficult to improve the controllability of the golf club and
reduce the variations in the directivity of the hit ball.
Examples
[0085] Next, the present invention will be described in detail on
the basis of Examples.
[0086] The materials of the shaft for the golf club fabricated in
Example 1 and Comparative Example 1 are shown below.
[0087] Prepreg A: carbon fiber prepreg MR350C100S (thickness of
0.084 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
[0088] Prepreg B: carbon fiber prepreg TR350E125S (thickness of
0.113 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
[0089] Prepreg C: carbon fiber prepreg MR350C150S (thickness of
0.127 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
[0090] Prepreg D: glass fiber prepreg GE352G135S (thickness of
0.111 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
[0091] Glass fiber-woven fabric prepreg: WPA 03104 EGE (prepreg
made by impregnating a woven fabric of a plain fabric having fabric
density of weft of 60/25 mm and waft of 51/25 mm, in which the warp
and the weft were glass fiber ECD 900 1/0 manufactured by Nitto
Boseki Co., Ltd., with epoxy resin composition; resin content rate
of 26 wt %, manufactured by Nitto Boseki Co., Ltd.)
[0092] Metal wire: amorphous metal fiber Bolfur flat wire 75FE10
(composition: Co/Fe/Cr/Si/B, shape: a cross section of a shape
which is bent at an intermediate height, like a bow with the
maximum thickness of 17 to 25 .mu.m and the width of 180 to 280
.mu.m; manufactured by Unitika Limited)
Example 1
[0093] <Manufacture of Glass Fiber-Woven Fabric Prepreg with
Metal Wires Interposed Therebetween>
[0094] By using the drum winding device 20 shown in FIG. 3, a
prepreg with the metal wires interposed therebetween was
manufactured (see a drum winding method disclosed in Japanese
Unexamined Patent Application, First Publication No. 2001-341126).
The drum winding device 20 includes an unwinding bobbin 11 rotating
and drawing out the metal wire 5 and a drum 13 for winding the
metal wire 5 drawn out from the unwinding bobbin 11. Further, the
drum winding device 20 includes a detector 14, disposed between the
unwinding bobbin 11 and the drum 13, for detecting tension applied
to the metal wire 5, and a brake 15 for controlling the rotational
speed of the unwinding bobbin 11 based on measured data of the
tension detected by the detector 14. In addition, the drum winding
device 20 includes a signal line 16 for transferring the measured
data of the tension detected by the detector 14 to the brake 15,
and a signal line 17 connecting the brake 15 and the unwinding
bobbin 11 and transferring a control signal from the brake 15 to
the unwinding bobbin 11. In this way, by controlling the rotational
speed of the unwinding bobbin 11, the tension applied to the metal
wire 5 is adjusted.
[0095] By using the drum winding device 20, the glass fiber woven
fabric prepreg was wound around the drum 13 in such a way that the
warp is disposed in a circumferential direction of the drum 13.
Next, the metal wires 5 were wound on the glass fiber woven fabric
prepreg at an interval of 2 mm. The winding angle of the metal
wires 5 was about 90 degrees with respect to the axial direction of
the drum 13. The tension applied to one metal wire 5 was 90 to 110
gf/metal wire.
[0096] Next, the glass fiber woven fabric prepreg wound with the
metal wires 5 was pressed by a rubber roller (not shown) to
pressurize the metal wires 5 and the glass fiber woven fabric
prepreg. It was detached from the drum 13, so that the prepreg, in
which the metal wires 5 were disposed on the glass fiber woven
fabric prepreg, was obtained.
[0097] Another sheet of separately prepared glass fiber woven
fabric prepregs was adhered to the surface of the glass fiber-woven
fabric prepreg, on which the metal wires 5 are disposed, in such a
way that the warp direction of the two sheets of glass fiber-woven
fabric prepregs intersects at 90 degrees. Two sheets of glass
fiber-woven fabric prepregs were compressed by applying a cylinder
pressure of 4.0 kgf/cm.sup.2 at a temperature of 68.degree. C. by
using a fusing press (manufactured by Nambu Iron works Co., Ltd.)
to obtain the glass fiber-woven fabric prepreg with the metal wire
interposed therebetween (hereinafter, referred to as `metal wire
prepreg`).
[0098] <Cutting and Winding of Prepreg>
[0099] The prepregs 31 and 33 were obtained by cutting the prepreg
A in the shapes indicated by [1] and [3] in FIG. 4. In this
instance, the prepreg 31 was formed by attaching two sheets of
prepregs A, which were cut to have the same size, in such a way
that the fiber direction intersects each other at an angle of 90
degrees, as indicated by f and g, in the state in which joint
positions were slightly deviated from each other. In the prepreg
33, the fiber direction was set in a direction indicated by i.
[0100] The prepreg B was cut in the shape shown in left sides of
[2], [5] and [6] in FIG. 4 to obtain the prepregs 32, 35 and 36. In
the prepreg 32, the fiber direction was set in a direction
indicated by h. In the prepreg 35, the fiber direction was set in a
direction indicated by k. In the prepreg 36, the fiber direction
was set in a direction indicated by m.
[0101] The prepreg C was cut in the shape shown in [4] in FIG. 4 to
obtain the prepreg 34. In the prepreg 34, the fiber direction was
set in a direction indicated by j.
[0102] The prepreg D was cut in the shape shown in [7] in FIG. 4 to
obtain the prepreg 38. In the prepreg 38, the fiber direction was
set in a direction indicated by q.
[0103] The metal wire prepreg manufactured by the above was cut in
the shape shown in a right side of [6] in FIG. 4 to obtain the
prepreg 37. In the prepreg 37, the fiber direction was set in
directions indicated by n and p. Further, the metal wire 5 was
interposed along the direction shown by p.
[0104] Next, the prepregs 31 to 38 were wound around the portion of
120 mm to 1310 mm from a smaller-diameter end of a cored mandrel 30
shown in [M] in FIG. 4 in the order of [1] to [7]. In this
instance, as the cored mandrel 30, one having an overall length of
1450 mm, a smaller-diameter end having a diameter of 3.3 mm, a
larger-diameter end having a diameter of 13.0 mm was used, in which
a portion of 950 mm from the smaller-diameter end to the
larger-diameter end side had a diameter of 12.8 mm and a portion of
1250 mm from the smaller-diameter end to the larger-diameter end
side had a diameter of 13.0 mm. Further, the prepreg 37 (sheet cut
from the metal wire prepreg) was wound to be 2.9.times.10.sup.2 mm
to 5.3.times.10.sup.2 mm which is measured from the larger-diameter
end of the shaft for the golf club.
[0105] Next, polypropylene tape (not shown) having a
heat-shrinkable property of 20 .mu.m at a width of 30 mm was wound
and fixed on the surface of the prepreg wound around the cored
mandrel 30 at a winding pitch of 2 mm to obtain a shaft tube formed
on the cored mandrel 30.
[0106] <Curing of Resin and Grinding of Surface of Shaft
Tube>
[0107] After the shaft tube was put in a curing furnace and then
was heated at a temperature of 145.degree. C. over 2 hours to
perform the curing process of the resin of the prepreg, the
polypropylene tape and the cored mandrel 30 were removed. Both ends
of the obtained shaft tube for a golf club were cut by 10 mm,
thereby obtaining a shaft having the overall length of 1170 mm, in
which the metal wires 5 were disposed at 2.8.times.10.sup.2 mm to
5.2.times.10.sup.2 mm from the larger-diameter end of the
shaft.
[0108] The shaft tube for the golf club was subjected to surface
finishing using a cylindrical grinding machine so that the outer
diameter of the smaller-diameter end was 8.50 mm and a cantilever
flex was 162 mm, thereby obtaining the shaft for the golf club
according to Example 1.
[0109] <Attaching of Golf Club Head and Grip>
[0110] A titanium golf club head (a volume of 430 cm.sup.3, weight
of 203 g and a loft angle of 10.5.degree.), which was commercially
available, for a driver was attached to the smaller-diameter end of
the shaft for the golf club according to Example 1 by using epoxy
resin adhesive. In addition, the larger-diameter end of the shaft
was cut by 75 mm to obtain the shaft with the metal wire 5 disposed
at 2.05.times.10.sup.2 to 4.45.times.10.sup.2 mm. A commercially
available rubber grip was attached to the shaft by using a
double-sided tape to obtain the golf club in Example 1.
[0111] <Evaluation of Hitting Ball>
[0112] Feeling evaluation was performed by 5 testers a to e (two
professional players and three upper grade amateurs) in which they
hit a golf ball with the golf club according to Example 1. The
feeling evaluation was a combined evaluation of three viewpoints on
(1) ease of swing, (2) ease in capturing of timing, and (3) whether
the bending state is a desired one. Comparative Example 1 was set
to `3` to be indicated as a comparative evaluation.
[0113] 5: very excellent
[0114] 4: excellent
[0115] 3: normal like Comparative Example 1
[0116] 2: inferior
[0117] 1: very inferior
[0118] Table 5 below shows evaluation results.
[0119] In addition, when 5 testers hit the golf ball by the golf
club according to Example 1, measurement of flying distance and
right and left deviation was performed by using `TrackMan`
(manufactured by Interative Sports Games) (input by 43 m/s as the
head speed and supposed that the hit point was adjacent to the
center portion of the head). The measurement was performed by
hitting three times with the exception of missed shots. As a
result, an average flying distance (carry) was 222.3 yrd, a
variation of the flying distances was .+-.3.6 yrd, and the right
and left deviation was .+-.8.2 yrd, so that the flying distance and
the directivity were excellent.
Comparative Example 1
[0120] The golf club according to Comparative Example 1 was
obtained by the same method as Example 1, except that the winding
sheet 37 (sheet cut by the metal wire prepreg in predetermined
dimensions) was not wound.
[0121] With respect to the shaft for the golf club according to
Comparative Example 1, bending rigidity, the crush-deformation
resistance, and crush withstand load were measured. The measured
results are shown in Table 3 below. The bending rigidity (EI
values) measured whenever the measuring point was moved to a
position of 100 mm to a position 925 mm from the larger-diameter
end of the shaft for the golf club at an interval of 50 mm in a
longitudinal direction of the shaft is shown in Table 4 below.
Further, FIG. 5 shows EI distribution illustrating a relation
between EI values and a distance from the larger-diameter end of
the shaft.
[0122] By using the golf club according to Comparative Example 1,
the feeling evaluation, the flying distance evaluation and the
right and left deviation evaluation were performed by the same
method as Example 1. The result of the feeling evaluations are
shown in Table 5 below. An average flying distance (carry) was
217.1 yrd, a variation of the flying distances was .+-.6.2 yrd, and
the right and left deviation was .+-.13.4 yrd, so that the flying
distance and the directivity were behind those of Example 1.
Examples 2 to 4 and Comparative Examples 2 to 7
[0123] The materials of the shaft for the golf club fabricated in
Examples 2 to 4 and Comparative Examples 2 to 7 are shown
below.
[0124] Prepreg A: carbon fiber prepreg TR350E125S (thickness of
0.113 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
[0125] Glass fiber-woven fabric prepreg: WPA 03 104 EGE (prepreg
made by impregnating a woven fabric of a plain fabric having fabric
density of weft of 60/25 mm and waft of 51/25 mm, in which the warp
and the weft were glass fiber ECD 900 1/0 manufactured by Nitto
Boseki Co., Ltd., with epoxy resin composition; resin content rate
of 26 wt %, manufactured by Nitto Boseki Co., Ltd.)
[0126] Metal wire: amorphous metal fiber Bolfur flat wire 75FE10
(composition: Co/Fe/Cr/Si/B, shape: a cross section of a shape
which is bent at an intermediate height, like a bow with the
maximum thickness of 17 to 25 .mu.m and the width of 180 to 280
.mu.m; manufactured by Unitika Limited)
[0127] The glass fiber woven fabric prepreg (metal wire prepreg)
with the metal wires interposed therebetween was manufactured by
the same method as Example 1.
[0128] <Cutting and Winding of Prepreg>
[0129] The prepregs 41, 43, 44, 45 and 46 were obtained by cutting
the prepreg A in the shapes indicated in [1], [2], [3], [4], [5]
and [6] in FIG. 4. In this instance, the prepreg 41 was formed by
attaching two sheets of prepregs A, which were cut to have the same
size, in such a way that its fiber direction intersects each other
at an angle of 90 degrees, as indicated by f and g, in the state in
which joint positions were slightly deviated from each other. In
the prepreg 43, the fiber direction was set in a direction
indicated by i. In the prepreg 44, the fiber direction was set in a
direction indicated by j. In the prepreg 45, the fiber direction
was set in a direction indicated by k. In the prepreg 46, the fiber
direction was set in a direction indicated by m.
[0130] The metal wire prepreg manufactured by the above was cut in
the shape shown in a right side of [6] in FIG. 4 to obtain the
prepreg 47 (metal wire prepregs A-1, A-2, A-3, A-4, B, C, D, E, and
F) shown in Table 1. In the prepreg 47, the fiber direction was set
in directions indicated by n and p. Further, the metal wire 5 was
interposed along the direction shown by p.
[0131] In Example 2, the metal wire prepreg A-1 in Table 1 was
used, in Example 3, the metal wire prepreg B was used, in Example
4, the metal wire prepreg A-2 was used, in Comparative Example 2,
the metal wire prepreg C in Table 2 was used, in Comparative
Example 3, the metal wire prepreg D was used, in Comparative
Example 4, the metal wire prepreg E was used, in Comparative
Example 5, the metal wire prepreg F was used, in Comparative
Example 6, the metal wire prepreg A-3 was used, and in Comparative
Example 7, the metal wire prepreg A-4 was used. In Comparative
Example 1, the prepreg 47 was not used.
TABLE-US-00001 TABLE 1 Example 2 Example 3 Example 4 Kind of metal
wire prepreg A-1 B A-2 Existence of metal wire present present
present Width of metal wire (.mu.m) 180-280 180-280 180-280
Interval of metal wires (mm) 2 4 4 Width of metal prepreg (mm) 240
240 160 Placed position of metal prepreg 205-445 205-445 245-405
(distance from larger-diameter end) (mm) Orientation angle of metal
wire (.degree.) 90 90 90
TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 4 5 6 7 Kind of
metal wire -- C D E F A-3 A-4 prepreg Existence of metal absent
present present present present present present wire Width of metal
wire -- 180-280 180-280 180-280 360-560 180-280 180-280 (.mu.m)
Interval of metal wires -- 6 2 4 4 2 2 (mm) Width of metal prepreg
-- 240 240 240 240 300 100 (mm) Placed position of -- 20-445
205-445 205-445 205-445 175-445 275-375 metal prepreg (distance
from larger-diameter end) (mm) Orientation angle of -- 90 <90
<90 90 90 90 metal wire (.degree.)
[0132] The glass fiber woven fabric prepreg was cut in the shape
shown in [7] in FIG. 4 to obtain the prepreg 48.
[0133] Next, the prepregs 41, 43, 44, 45, 46, 47 and 48 were wound
around the portion of 75 mm to 1265 mm from a smaller-diameter end
of a cored mandrel 30 shown in [M] in FIG. 4 in the order of [1] to
[7]. In this instance, as the cored mandrel 30, one having an
overall length of 1500 mm, a smaller-diameter end having a diameter
of 5.0 mm and a larger-diameter end having a diameter of 13.5 mm
was used, in which a portion of 1000 mm from the smaller-diameter
end to the larger-diameter end side had a diameter of 13.5 mm.
Further, the prepreg 47 (sheet cut from the metal wire prepreg) was
wound to be 2.9.times.10.sup.2 mm to 5.3.times.10.sup.2 mm which is
measured from the larger-diameter end of the shaft of the golf
club.
[0134] Next, polypropylene tape (not shown) having a
heat-shrinkable property of 20 .mu.m at a width of 30 mm was wound
and fixed on the surface of the prepreg wound around the cored
mandrel 30 at a winding pitch of 2 mm to obtain a shaft tube formed
on the cored mandrel 30.
[0135] <Curing of Resin and Grinding of Surface of Shaft
Tube>
[0136] After the shaft tube was put in a curing furnace and then
was heated to a temperature of 145.degree. C. for 2 hours to
perform the curing process of the resin of the prepreg, the
polypropylene tape and the cored mandrel 30 were removed. Both ends
of the obtained shaft tube for a golf club were cut by 10 mm,
thereby obtaining a shaft having the overall length of 1170 mm, in
which the metal wires 5 were disposed at 2.8.times.10.sup.2 mm to
5.2.times.10.sup.2 mm from the larger-diameter end of the
shaft.
[0137] The shaft tube for the golf club was subjected to surface
finishing using a cylindrical grinding machine so that the outer
diameter of the smaller-diameter end was 8.50 mm and a cantilever
flex was 192 mm, thereby obtaining the shafts for the golf club
according to Examples 2 to 4 and Comparative Examples 2 to 7.
[0138] With respect to the shaft for the golf clubs according to
Examples 2 to 4 and Comparative Examples 2 to 7, bending rigidity,
the crush-deformation resistance, and crush withstand load were
measured. The measured results are shown in Table 3.
TABLE-US-00003 TABLE 3 Comp Comp Comp Comp Comp Comp Comp Ex. 2 Ex.
3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Load 71.3 70.9
74.4 40.0 71.2 66.2 64.5 72.7 77.7 68.0 variation .DELTA.P(kgf)
Time(sec) 42 44 48 41 42 43 41 34 47 44 Crush 1.40 1.47 1.60 1.37
1.40 1.43 1.37 1.13 1.57 1.47 deformation .DELTA..lamda. (mm) Width
of test 20 20 20 20 20 20 20 20 20 20 piece (mm) Crush-deformation
2.55 2.42 2.33 1.46 2.26 2.24 2.28 3.21 2.48 2.32 resistance Rc
(kgf/mm.sup.2) Crush 71.4 70.9 74.4 65.9 73.2 68.2 65.7 86.9 78.0
77.5 withstand load (kgf)
[0139] Further, the bending rigidity (EI values) measured whenever
the measuring point was moved to a position of 100 mm to a position
925 mm from the larger-diameter end of the shaft for the golf club
at an interval of 50 mm in a longitudinal direction of the shaft is
shown in Table 4 below. Further, FIGS. 6 to 8 show EI distribution
illustrating a relation between EI values and a distance from the
larger-diameter end of the shaft according to Examples 2 to 4, and
FIGS. 9 to 14 show the above EI distribution according to
Comparative Examples 2 to 7.
TABLE-US-00004 TABLE 4 Measuring point from Bending rigidity
EI(.times.10.sup.6 kgf mm.sup.2) larger-diameter Comp Comp Comp
Comp Comp Comp Comp end (mm) Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3
Ex. 4 Ex. 5 Ex. 6 Ex. 7 100 5.5 5.6 5.6 5.5 5.6 6.1 5.9 5.7 5.7 5.6
125 5.4 5.5 5.6 5.5 5.5 6.0 5.9 5.6 5.7 5.5 175 5.5 5.7 5.5 5.3 5.6
5.8 5.8 5.7 5.8 5.4 225 5.7 5.8 5.5 5.1 5.7 5.8 5.7 5.9 5.8 5.2 275
5.4 5.5 5.3 4.9 5.4 5.4 5.4 5.7 5.4 5.1 325 5.1 5.1 4.9 4.5 5.0 5.0
5.1 5.3 5.1 4.9 375 4.7 4.7 4.4 4.2 4.6 4.7 4.7 4.9 4.7 4.4 425 4.2
4.2 3.9 3.9 4.2 4.2 4.2 4.4 4.2 3.9 475 3.7 3.7 3.5 3.6 3.7 3.8 3.6
3.8 3.8 3.5 525 3.2 3.2 3.2 3.3 3.2 3.4 3.3 3.4 3.3 3.2 575 2.9 2.9
2.9 3.0 2.9 3.1 3.0 3.0 2.9 2.9 625 2.6 2.6 2.6 2.7 2.6 2.8 2.7 2.7
2.6 2.6 675 2.4 2.4 2.4 2.4 2.4 2.5 2.4 2.4 2.4 2.4 725 2.1 2.1 2.1
2.2 2.1 2.3 2.2 2.2 2.1 2.2 775 1.9 1.9 1.9 2.0 1.9 2.0 2.0 2.0 1.9
2.0 825 1.8 1.8 1.8 1.9 1.8 1.9 1.9 1.9 1.8 1.8 875 1.7 1.7 1.8 1.8
1.7 1.8 1.8 1.8 1.7 1.8 925 1.6 1.6 1.6 1.7 1.6 1.7 1.7 1.7 1.6
1.6
[0140] In Comparative Examples 1 to 7, the crush-deformation
resistance was less than 2.3 kgf/mm.sup.2 or more than 2.6
kgf/mm.sup.2, the bending rigidity of the portion of 125 to 175 mm
from the larger-diameter end of the shaft was more than
5.7.times.10.sup.6 kgfmm.sup.2, and the bending rigidity of the
portion of 225 to 275 mm from the larger-diameter end of the shaft
was less than 5.3.times.10.sup.6 kgfmm.sup.2. By contrast, in
Examples 2 to 4, the crush-deformation resistance was 2.3
kgf/mm.sup.2 or more and 2.6 kgf/mm.sup.2 or less, the bending
rigidity of the portion of 125 to 175 mm from the larger-diameter
end of the shaft was more than 5.7.times.10.sup.6 kgfmm.sup.2 or
less, and the bending rigidity of the portion of 225 to 275 mm from
the larger-diameter end of the shaft was 5.3.times.10.sup.6
kgfmm.sup.2 or more.
[0141] <Attaching of Golf Club Head and Grip>
[0142] A titanium golf club head (a volume of 460 cm.sup.3, weight
of 195 g and a loft angle of 9.0.degree.), which was commercially
available, for a driver was attached to the smaller-diameter end of
the shaft for the golf club according to Example 1 by using epoxy
resin adhesive. In addition, the larger-diameter end of the shaft
was cut by 75 mm to obtain the shaft with the metal wire 5 disposed
at 2.05.times.10.sup.2 to 4.45.times.10.sup.2 mm. A commercially
available rubber grip was attached to the shaft by using a
double-sided tape to obtain the golf clubs in Examples 2 to 4 and
Comparative Examples 2 to 7.
[0143] Conditions of the golf clubs are as follows:
[0144] Club length: 45.2 inches (1148 mm)
[0145] Club weight in total: 300 g
[0146] Club balance: D0
[0147] Club vibration frequency: 227 cpm
[0148] Head volume: 460 cc
[0149] Head weight: 195 g
[0150] Loft angle: 9.degree.
[0151] The club balance is a value calculated by obtaining a length
(inch) from a gravity point of the golf club to a fulcrum point by
using a prorythmic scale in which the larger-diameter end of the
grip and a position of 14 inches from the larger-diameter end are
assumed to be fulcrum points, and then multiplying the length
(inch) from the gravity point to the fulcrum point by the club
weight (ounce). It is defined that D0 is a reference value when a
value is 213.5, and if a value is increased or decreased by 1.75,
one point is increased or decreased.
[0152] <Evaluation of Hitting Ball>
[0153] Feeling evaluation on the golf club according to Examples 2
to 4 and Comparative Examples 2 to 7 was performed by the same
method as Example 1. The evaluation results are shown in Table
5.
TABLE-US-00005 TABLE 5 Result of feeling evaluation Example/
(Comparative Example 1 was set to Comparative Kind of metal `3` for
a comparative evaluation Example wire prepreg a b c d e average
Comparative -- 3 3 3 3 3 3.0 Example 1 Comparative C 1 4 3 4 4 3.2
Example 2 Comparative D 2 1 2 2 4 2.2 Example 3 Comparative E 4 2
3.5 5 3 3.5 Example 4 Comparative F 3 2 4 3 3 3.0 Example 5 Example
1 A-1 4 4 4 2 4 3.6 Example 2 A-1 5 4 5 3 3 4.0 Example 3 B 4 5 3.5
4.5 3 4.0 Example 4 A-2 2 4 5 2 4 3.3 Comparative A-3 1 1 2 4 4 2.4
Example 6 Comparative A-4 2 2 3 5 2 2.8 Example 7
[0154] As compared with Comparative Examples 1 to 7, the
evaluations of Examples 2 to 4 were high, and thus the results were
obtained in which the golf club using the shaft for the golf club
according to the present invention has a good feeling when
used.
[0155] Further, the flying distance and the right and left
deviation in the golf clubs according to Examples 2 to 4 and
Comparative Examples 1 to 7 were measured by the same method as
Example 1. The results of flying distance and the right and left
deviation are shown in Table 6.
TABLE-US-00006 TABLE 6 Average of flying Right and left deviation
distance (yrd) (SD) (yrd) Comparative Example 1 220.8 17.4
Comparative Example 2 220.7 15.3 Comparative Example 3 221.9 16.6
Comparative Example 4 221.1 17.7 Comparative Example 5 222.0 16.2
Example 2 232.7 13.3 Example 3 229.0 11.1 Example 4 226.4 8.5
Comparative Example 6 220.2 23.4 Comparative Example 7 224.9
15.9
[0156] The average flying distance of the hit ball was about 220
yrd in Comparative Examples 1 to 7, but the average flying distance
was increased to about 230 yrd in Examples 2 to 4. Further, the
right and left deviation was 17.5 yrd in standard variation in
Comparative Examples 1 to 7, but the right and left deviation was a
low value of 11.0 yrd in Examples 2 to 4. In addition, in order to
statistically show an apparent boundary line between Comparative
Examples and Examples, as a result of using the Wilcoxon sign-rank
test, there was a significant difference of P<0.01 in the flying
distance and P<0.05 at a landing point of right and left
directions.
[0157] From the above results, in the case in which the shaft for
the golf club according to the present invention is used in the
long-sized golf club having a club length of 45.2 inches, the use
feeling was good, the flying distance of the hit ball was improved,
and the variation in the directivity of the hit ball was
reduced.
* * * * *